Contracts director Andrew Smith said: "When we first got to the site it seemed huge, none of us had seen anything like it before. Fifty thousand man hours later, we realised how important it was to be part of a good team."

Smith said logistics were a challenge from the start. Deliveries had to be booked 48 hours in advance and "go into quarantine" on the M11 to be checked by security.

Once on-site, contractors had 36 hours to unload deliveries, planting one-and-a-half semi-mature trees per hour to meet the deadline.

He said the wetlands was "the most demanding project", not helped by waterlogged ground, snow and rain. "Within two weeks, it was apparent the deadlines weren't going to be met."

So the company coconut-wrapped the trees, finished in July 2011 and deferred wildflower planting until the autumn. "Expectations were demanding," Smith added.

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